Praying like your future depended on it

Isaac prays for his wife Rebekah to have children.  20 years go by from the time they were married until the twins are born... at what point did Isaac start praying?
His dad is still alive, having new kids with a new woman... is Isaac really the one God is going to use to raise up a people for God?  What is God doing?
We should be praying as if our prayer life was what held our life and vision together, and allowing God to keep us on track as we pray through His Word, ad we pray for those things He puts on our hearts, and those things He clearly tells us to pray about and for.  So go pray.